When broadcasting energy such as with television broadcast, radio broadcast, radar or other emissions, energy is radiated from a broadcast point to provide electronic transmissions to consumers or other receivers. For example, in the television broadcast industry, the television signal is beamed from towers having antennae or broadcast arrays designed to reach a specific coverage area. In constructing a broadcast tower with an antenna array affixed to the top, there is a relationship between the height of the tower, the shape of the beam, the gain of the antenna, the specific array elements, the mechanical or electrical tilt, the cost of the tower, and the broadcast area reached. Generally, the higher the tower, the larger the broadcast area. However, the higher the tower, the higher the cost. Therefore, it is desirable to have a tower height that sufficiently reaches the desired broadcast area while keeping the height to a necessary minimum for such broadcast.
Additionally, the broadcast area can be increased by increasing the strength of the signal emitted and, therefore, the strength of the transmitter. Again, however, the greater the strength, the higher the cost. One specific factor affecting the performance of the broadcast array is the tilt of the broadcast array or beam tilt. This factor plays a significant role in the coverage area of the antenna. By optimizing the beam tilt, an optimal coverage area can be achieved without solely relying upon tower height or transmission strength. Accordingly, there is a need to be a reliable and informative way of analyzing broadcast areas so as to maximize the broadcast area while minimizing the cost.
Traditionally, it is known to analyze the broadcast area, or coverage, by using a Longley-Rice analysis model. The Longley-Rice model was developed in 1978 and is applied to point-to-point communications over varying terrain. The Longley-Rice model predicts long-term median transmission loss over an irregular terrain pattern relative to the free-space transmission loss. This means that the Longley-Rice model allows the calculation of broadcast area according to the specific terrain or geographical and physical features of the target area and the characteristics of the antenna itself. For example, buildings, hills, and other solid structures will affect the broadcast area coverage while having flat open plains renders a different result. Field strength is predicted using the path of the terrain and the relativity of the troposphere. The signal strength within the radio horizon is calculated according to the prediction of interference from obstacles based on a fresnel-kirchof's knife-edge. Unfortunately, the Longley-Rice method performs its calculations based upon the center point of the transmission beam and assumes that transmissions are one-dimensional. Clearly, the physical realities of a transmission beam are that it radiates from the source of origin as a true propagating wave and is certainly not one-dimensional. Therefore, an analysis model is needed to consider the fact that a transmission is three-dimensional, at least, rather than the traditional and theoretical one-dimensional model.
Accordingly, it is an object of this invention to provide for an analysis method for calculating broadcast areas based on beam tilt of a particular tower height and transmission strength so that the most advantageous beam tilt for the broadcast area can be determined.
It is yet another object of this invention to provide an analysis method that takes into account the physical realities of energy transmissions operating on three dimensions.
It is yet another object of this invention to provide for an easy-to-use analysis method with easily viewable results so as to assist in the determination of the broadcast area based upon an antenna's characteristics.